Presentations

Recent studies on green roof water quality have indicated that extensive green roof systems are a source for phosphorus, and occasionally a source for nitrogen as compared to conventional roofing systems. Due to the presence of soil media and vegetation on green roofs, a comparison to traditional roofs reveals little about relative nutrient quantities released. The Villanova green roof was compared to other suburban vegetated areas for nutrient export. The water quality parameters evaluated included nitrogen and phosphorus species, chlorides, total suspended solids, and total dissolved solids. Where applicable, US EPA recommended nutrient criteria for rivers and streams, and for lakes and reservoirs, were used as a reference point to nutrient parameters. Results indicated that the green roof generally retained nitrogen and released phosphorus; its performance was similar to or better than that of a grassy area and a wooded area in terms of nutrient retention, and performed similarly to an area that was at least 50% impervious. In addition, a comparison of quality data from overflow samples revealed that a nearby wetland and rain garden outperformed the green roof in terms of nutrient retention. It is suggested that if nutrient export is a concern and space is available, green roof overflow could be diverted to other stormwater control measures which are designed to remove excess nutrients from stormwater runoff.

Rain gardens are vegetated stormwater control measures (SCMs) that reduce runoff volume and high peak flows. Rain gardens promote infiltration and evapotranspiration (ET), thus mitigating the effects of high stormwater runoff that have become common in developed areas. In addition to runoff quantity, rain gardens also help improve water quality by allowing water to infiltrate into an engineered or native soil media. Engineered soils typically contain a high sand content with lower amounts of silts, clays, and organics. Native soils can be used if the hydraulic properties indicate that an adequate infiltration rate is attainable. Additionally, to save construction costs, engineered soils can be mixed with native soils. Rain gardens may also contain a liner and an underdrain. Systems without a liner allow for evapotranspiration and infiltration into the native soil layer, which promotes recharge to the underlying aquifer. Systems with a liner and underdrain typically favor evapotranspiration.

A study was proposed to determine the best rain garden design and configuration for optimum hydrologic performance. This included the use of a liner, the use of an underdrain, soil media, and age of the rain garden. Many rain gardens on Villanova University’s campus were considered, and three rain gardens were selected: the Bioinfiltration Traffic Island, Fedigan Rain Gardens, and Pavilion Traffic Island. The three sites have notably different configurations, soil mixtures, and other defining characteristics. After site investigations, instrumentation was selected for each site, which included pressure transducers, soil moisture sensors, and rain gages. This talk will describe the challenges and soil properties encountered during the site investigations, as well as the process of instrumentation and equipment selection for each site.

Funded by the EPA Urban Waters Small Grant program, the project's purpose is to design, construct and monitor two shelters (e.g. bus shelter or picnic table covering) with vegetated roofs in the Darby Creek watershed in southeastern Pennsylvania. The shelters will be living laboratories used for community education and stormwater research. The research component will focus on green roof performance for different configurations of growing media, plants, drainage designs and more. The education component includes collaboration with the Eastern Delaware County Stormwater Collaborative and Upper Darby High School to introduce community members to green roof technologies and introduce students via the science curriculum to the hydrologic processes of green roofs.

A key component of these living laboratories is to precisely and accurately measure the inputs and outputs of the green roof to quantify performance. The magnitude of outflow (drainage) measurements is relatively small for these small-scale green roofs, thus requiring a custom solution to measure outflow. The presentation will give an overview of the project goals and also focus on the method developed for runoff measurement from the green roofs.

Infiltration trenches are a stormwater control measure (SCM) used in urban and ultra-urban areas to provide stormwater runoff volume reduction. Legacy infiltration trenches are difficult if not impossible to maintain and were often built without pretreatment. As runoff with high suspended solid loads enters an infiltration trench there is continual buildup of solids that clog the infiltrating surface, decreasing the hydraulic conductivity at the soil interface and the performance and longevity of these systems.

The present study builds on previous work at Villanova University on an extremely undersized infiltration trench (directly connected impervious drainage area to SCM area of 160:1) to artificially accelerate annual loading to evaluate long-term performance. Ten years and 1270 cm of rain later, infiltration through the bottom of the trench has ceased and the sides have slowed as well. Recession rates have reached an equilibrium point where they no longer improve or decrease. Although recession rates have slowed considerably since 2004, reduced infiltration still occurs in the bottom layer of the IT.

Green roofs are an effective, yet costly stormwater control measure that reduces runoff volume through ET, and can provide other services, such as improved building insulation and reduced urban heat island effect. For green roof systems to be competitive as a low impact development strategy, they must be designed to maximize ET. Understanding each component’s process in a green roof design is the key to designing a green roof to perform optimally.

Evapotranspiration (ET) is a primary mechanism for removal of water in a green roof. When adequate water is available, the ET rate is limited by the energy-available. However, when the system is water-limited then less ET will occur than is climatologically possible, thus causing the green roof to perform sub-optimally. One way to retain more water within the green roof is to minimize drainage (outflow) by altering or restricting the drainage layer within a green roof. In the present work, a green roof with a drainage layer is compared to a lysimeter without a drainage layer to determine if hydrologic performance is enhanced or compromised in either system.

Preliminary results from the Villanova University green roof systems show that the under drained system has approximately 65% of rainfall go to ET, while the undrained system showed 77% ET from April through November 2013. However, the system without drainage has seen as high as 88% annually go to ET in drought years. Additionally, the plants appeared healthier during the drought in the undrained system than in the drained system.

As sectors shaping the built environment increasingly credit the non-stormwater benefits of green stormwater infrastructure (GSI), decision-makers at all levels will recognize shared value opportunities that exist in infrastructure renewal projects which also address “up-stream” sustainability goals. In this presentation, emerging developments in field of sustainability are highlighted within the infrastructure sector - specifically stormwater management – to show how developing integrated planning and design tools may accelerate the broader paradigm shift already occurring within the infrastructure sector: designing for shared value. Among others, examples of system level shared value opportunities include designs for low-carbon stormwater control, maximizing other non-stormwater benefits, and designing for adaptive reuse. A review of three established or emerging tools (life cycle assessment - LCA, triple-bottom-line (TBL) analysis, and STEEP assessment), their applicability, and their potential when scaled across industry are discussed using GSI examples.

Stormwater control measures (SCMs) are built in order to address the issues of stormwater runoff. These issues are primarily focused around volume control and water quality treatment. There is limited research on water temperature as a stormwater pollutant and how SCMs should be constructed to treat it. The constructed stormwater wetland (CSW) at Villanova University has demonstrated to be a high-performing SCM in the areas of storm peak flow reduction (~72%) and with numerous water quality parameters (Total Nitrogen ~41% reduction during storms). Temperature was studied on the basis of storm events and monthly statistics from April to September 2014. The analysis revealed the strong influence of air temperature on inlet and outlet water temperatures, as well as how the CSW responds to heated runoff during storms.

Rain gardens are an approach to the development of green stormwater infrastructure (GSI) in private and public properties around the USA. A complete soil characterization of the unsaturated zone is required to design a stormwater control measure (SCM). This research project examined the plastic properties and the soil water characteristic curve (SWCC) of a set of engineered soils in a cluster of rain gardens in a tract development in Glasgow, Delaware. The soil samples were examined and classified using: soil gradation (USCS ASTM D2487 and USDA), Atterberg limits (ASTM D4318-10e1), chilled mirror hygrometer (ASTM D6836), and tensiometer range moisture characteristic curve using HyProp. The analyses indicated that the soil’s plasticity in the two failed rain gardens affected the infiltration capacity of the soils; this was not evident through the soil gradation alone.

As cities become more dense, green roofs are becoming a popular stormwater control measure for mitigating the impact of smaller rain events. While green roofs provide many benefits beyond stormwater control, such as improved building insulation and reducing the urban heat island effect, they are expensive and often times cannot compete with cheaper alternatives. In order to make green roofs a more viable option for property owners, they must be designed to take full advantage of their capabilities.

Evapotranspiration (ET) is a substantial component of the water balance in a green roof. The ET rate is an energy process when there is adequate water available. However, if the system is water-limited then less ET will occur than is climatologically possible, thus causing the green roof to perform sub-optimally. One way to retain more water within the green roof is to minimize drainage (outflow) by altering or restricting the drainage layer within a green roof. A system with a drainage layer is compared to a system without a drainage layer to determine if performance is enhanced or compromised in either system.

Preliminary results from the Villanova green roof show that the drained system has approximately 60-70% of rainfall go to ET, which is similar to the weighing lysimeter without a drainage layer. However, the weighing lysimeter without drainage has seen as high as 88% annually go to ET in drought years. Additionally, the plants appeared healthier during the drought in the undrained system than in the drained system. A fundamental question is whether adding the underdrain reduces or enhances this performance.

Stormwater control measures (SCMs) are typically designed for smaller events (e.g., 2.5 cm or the 2-year event) and are not always considered for larger, more extreme event management. The platform for this research is a green infrastructure treatment train consisting of linear vegetated SCMs ending in an infiltration trench designed for the 2.5 cm rainfall event. The results from two years of monitoring the treatment train have been quite surprising. The system has consistently met the volume reduction design goals and often exceeded them by significantly contributing to storm runoff mitigation during large extreme events. The treatment train system captured and removed at least 59% of the volume of every storm event analyzed from July 2012 through June 2014, with an average of 93% for events greater than the design volume of 2.5 cm. The analysis focuses on the infiltration trench performance and includes the effect of storm volume, duration, intensity and antecedent dry time. Furthermore, there were 159 storm events totaling 259 cm of rainfall during the study period. Given the drainage area loading, approximately 2,391 m3 of rainfall entered the linear vegetated component with approximately 420 m3 (18%) reaching the infiltration trench and only 103 m3 (4%) of rainfall determined to overflow from the system. Performance suggests that SCMs can be considered and credited in flood mitigation strategies.

Technology for stormwater treatment has different challenges from water treatment and wastewater treatment. First, the stormwater control measure needs to be applied throughout the watershed, such that maintenance is infrequent on these disperse practices. Second, the water to be treated tends to flow more infrequently than water or wastewater, resulting in a different paradigm for stormwater control measures. Still, much can be learned from water and wastewater treatment processes as long as these two challenges are taken into account, because stormwater treatment is, in comparison, in its infancy.

This talk will discuss three technologies (gismos) that have been developed for stormwater treatment to assist in the choice of stormwater control measures: first, a falling head infiltrometer that can be used to determine the saturated hydraulic conductivity at multiple locations simultaneously; second, a baffle that will turn a standard sump into a stormwater control device; third, an enhanced sand filter that will remove phosphate from stormwater runoff before it reaches the receiving water body. The challenges of stormwater treatment will be discussed en route.

The need to quantify the rates of evapotranspiration (ET) and infiltration in stormwater control measures (SCMs) is to properly accredit the systems’ volume reduction. At Villanova University, weighing lysimeters have been constructed to represent three different rain garden configurations in a side by side comparison of their ET and infiltration volume reduction potential. Two different soil media were implemented, as well as two different drainage regulation devices. The three lysimeters consist of native plants in a lined soil media basin with an underdrain that is attached to a drainage configuration.

Flow into the system is measured by a rain gage, soil moisture is measured through the soil column, and flow out of the system via ET and infiltration is measured to provide a comprehensive view of how water is moving through each of the systems. The monitoring system includes soil moistures meters located at 10 cm, 35 cm, and 65 cm depths in each lysimeter. Evapotranspiration loss is determined by a system mass balance via a tension load cell that measures the systems weight at 5 min intervals. Each lysimeter’s drainage regulation system is monitored for exfiltration with a custom-made flow rate device. To simulate the volume of rainfall a rain garden would obtain from the runoff of the surrounding catchment area, a distribution system that provides for a 5:1 and 10:1 impervious area: SCM area rainfall event was developed.

Bioinfiltration stormwater control measures (SCM’s) perform volume reduction of stormwater runoff through both infiltration and evapotranspiration (ET) mechanisms. However, the current state of practice in field of stormwater is heavily-tailored towards crediting infiltration and using it as the primary mechanism from which sizing and other design considerations are based. In the natural hydrologic cycle, this is not necessarily the case – as volume reduction from ET depends on rainfall distribution and climate-sensitive parameters and can account for a significant percentage and, at times, the majority of volume reduction. While methods exist to estimate potential ET using climatological parameters, a water balance approach seeks to quantify actual ET performance though conservation of mass entering and leaving the system. Quantification of actual ET performance (for instance, during storm events of varying intensity or with varying site conditions) will help establish a better basis to account for ET and create conditions where the role of ET has a larger influence in SCM design.

The utilization of life cycle analysis (LCA) in the area of green infrastructure is becoming a developing practice. Research from Flynn (2011) showed that impacts vary greatly between the life cycle phases – construction, operational life, and decommissioning phases – and reinforced the recognition of stormwater goals being part of a larger picture. Considering the scale at which green infrastructure is being adopted today (Philadelphia Water Department’s Green City Clean Waters program is an appropriate example), the scale of life cycle impacts (or avoided impacts) becomes increasingly important. Selection, siting, and design of SCM’s depend greatly on site-specific goals and, in many cases, the cost of implementation. Applied at scale, the pairing of LCA findings with site-specific characteristics (property values, site conditions, non-stormwater-related goals, etc.) can help encourage more holistic decision-making in the field of green infrastructure. A preliminary case study for bioinfiltration SCMs shows that the role and valuation of ET in green infrastructure design carries potential to significantly influence these costs and associated impacts.

Green roofs are often times under credited for stormwater volume reduction. However research has shown that volume reduction due to evapotranspiration (ET) can account for a significant portion of the water balance. Villanova’s Green Roof was constructed in the summer of 2006 atop the Center for Engineering Education and Research, and has been continuously monitored since 2009. Past research has focused on quantifying potential ET from an un-drained weighing lysimeter on the roof. With the installation and calibration of outflow measuring instrumentation, future investigations will focus on comparing the ET measurements of the lysimeter to the performance of the entire green roof with a drainage system. Using preliminary data for over 4 months, including data from more than 10 storms of varying size, analysis has shown very similar water balances for both the green roof and the lysimeter.

There has been limited research performed to measure the effects and performance of SCMs in series. As a result, in 2011, Villanova University constructed a treatment train which combines four SCMs to study the quantitative hydrologic and water quality effect on rainfall runoff of SCMs in series. The treatment train includes a vegetative swale, two rain gardens in series, and an infiltration trench. Research at the treatment train continues to focus on accurately quantifying the flow of rainfall runoff through the system. New instrumentation has been tested and implemented to provide accurate rainfall runoff inflow to the system. Further research will focus on accurately quantifying outflow of the system, as well as individual performance of SCMs in the system.

A yearlong study demonstrated the potential of native algae for bioremediation and biofuel production in the Villanova Constructed Stormwater Wetlands and Dundale Pond. The algae have been shown to play a key role in the removal of both inorganic nitrogen and inorganic phosphorus that enter the system. This study also visually demonstrated the existence of a frequent growth and flush cycle. During low flow conditions, algae growth is accelerated by the mild current, raised temperatures and low depth. These periods of low flow are occasionally interrupted by storm events that can raise the water level of the wetland several feet. These high flow storm events eliminate most of the algae in the wetland, carrying organics, nutrients and their BOD downstream. To analyze the potential of these algae as a biofuel feedstock, a proximate analysis of the algae samples was completed. The lipid, volatile matter, lignin and ash content was compared to current commercial grade algae species and the prominent algae found in the wetland forebay was found to be similar in composition. In addition, fast pyrolysis was completed to characterize the algae by identifying its chemical composition. These tests provide evidence that the native alga most at risk for the growth and flush cycle is also the species most suitable for biofuel conversion. Therefore, there may be potential for a stormwater style system that optimizes algal growth and that collects biomass as a biofuel feedstock before export.

Rain gardens use natural processes, such as infiltration and evapotranspiration, to control runoff from rain events. Although prior research has shown that rain gardens are effective at controlling the volume of runoff and pollutants associated with runoff, the extent of ground water mounding under rain gardens remains a concern for landowners, practitioners, and regulators. A rain garden on Villanova University’s campus was instrumented with monitoring wells to observe the influence of the rain garden on the water table. This rain garden receives the runoff from approximately 0.52 ha that consists of grassy areas as well as parking lots. In this presentation we will discuss the vertical and lateral behavior of localized mounding caused by infiltration in our rain garden subsequent to a storm event. The data used for the analysis was selected from one-and-a-half years of continuous monitoring at the site. A statistical model was developed, describing event-based peak ground water rise as a function of radial distance from the rain garden’s center and infiltrated water depth. Statistical analysis was performed to demonstrate significance of the model parameters. Analysis of time to peak and time to dissipate was performed. The system exhibited a very pronounced dissipation behavior in peak rise, normalized to infiltrated depth of water, with increase in radial distance. Temporal lag in mounding peak and dissipation was investigated with respect to radial distance. In light of the observed behavior, a methodology for estimating site-specific vertical and lateral impact was proposed. The methodology was applied to the rain garden, and the results reviewed in the context of geo-specific design storm.

Villanova University's Constructed Stormwater Wetland was recently reconstructed in 2010 to improve treatment efficiency by adding meanders to hold runoff in the treatment system longer. Water quality and quantity is measured throughout the year to monitor treatment performance. Further, dye tracer tests are being done to estimate the hydraulic residence time on a seasonal basis and for different flow conditions. Having a better understanding of system hydraulics will enable an improved stormwater sampling protocol and understanding of overall system performance.

PDH -;As per Pennsylvania's PE Act 25 Section 4.5c (d) (iv);One hour of professional development in course work, seminars or professional, technical presentations made at meetings, employer-sponsored courses, conventions or conferences shall equal one PDH unit. Note that it is the applicant’s responsibility to track their participation. This form is provided for your convenience.

Student presentations have been recorded since late 2009. These presentations can be found here.

VUSP is one of the five reserach areas that constitute the Villanova Center for the Advancement of Sustainability in Engineering (VCASE).

VCASE hosts lecture series during Fall and Spring semesters and invites external people to give a talk related to sustainability issues. One can view these talks either online or can plan to attend in person.